In some dual damascene patterning schemes, after via patterning a via-fill step is used to protect the via bottom from early breakthrough during the subsequent dual damascene trench etch. Organic or inorganic materials, such as bottom anti-reflective coatings (BARC), are commonly used to fill the via.
However, with the continuously shrinkage in feature size, this via-first scheme will face difficulty in finding a suitable via-fill material to achieve bubble-free filling and to effectively remove the via-fill material after etching. Additionally, with the implementation of borderless via structures, masking will also face greater challenges in achieving an aligned dual damascene structure.
U.S. Pat. No. 6,380,096 B1 to Hung et al. describes a via-first process using an anti-reflective coating (ARC) layer.
U.S. Pat. No. 6,350,675 B1 to Chooi et al. describes a process for simultaneously etching a via and a trench using silylated photoresist.
U.S. Pat. No. 6,133,144 to Tsai et al. describes a self-aligned dual damascene process.
U.S. Pat. No. 6,087,252 to Lu describes a process of forming a via plug and an interconnect simultaneously.